Connected: An Internet Encyclopedia
RFC 1583 - A.4 Link state advertisement formats

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### A.4 Link state advertisement formats

There are five distinct types of link state advertisements. Each link state advertisement begins with a standard 20-byte link state advertisement header. This header is explained in Section A.4.1. Succeeding sections then diagram the separate link state advertisement types.

Each link state advertisement describes a piece of the OSPF routing domain. Every router originates a router links advertisement. In addition, whenever the router is elected Designated Router, it originates a network links advertisement. Other types of link state advertisements may also be originated (see Section 12.4). All link state advertisements are then flooded throughout the OSPF routing domain. The flooding algorithm is reliable, ensuring that all routers have the same collection of link state advertisements. (See Section 13 for more information concerning the flooding algorithm). This collection of advertisements is called the link state (or topological) database.

From the link state database, each router constructs a shortest path tree with itself as root. This yields a routing table (see Section 11). For the details of the routing table build process, see Section 16.

A.4.1 The Link State Advertisement header
A.4.2 Router links advertisements
A.4.3 Network links advertisements
A.4.4 Summary link advertisements
A.4.5 AS external link advertisements

Next: A.4.1 The Link State Advertisement header

Connected: An Internet Encyclopedia
RFC 1583 - A.4 Link state advertisement formats